Refractive or reflective optical sights are used in a wide variety of applications to obtain increased magnification of a scene. In one common application, a viewing and aiming scope is affixed to the upper side of a rifle-type weapon used by a soldier or a hunter. The user sights through the viewing and aiming scope to acquire a target and aim the weapon toward the target to increase the likelihood of hitting the target with a projectile fired from the weapon.
One of the problems associated with a fixed-magnification viewing and aiming scope is that the field of view is limited and fixed. The larger the magnification of the scope, the smaller is the field of view. Even when the magnification is unity (1×), as in a reflex scope, the field of view of the scope is still a small fraction of the effective field of view of the unaided eye. Consequently, it can be difficult for the user to acquire a peripheral target through the viewing and aiming scope. One possibility is to take the eye away from the scope to acquire the target with the unaided eye, and then to look through the scope to aim, if the target is at a distance and is not moving too rapidly. The movement of the head and the need to adjust the eye to the scope image take time. Another possibility is to use a variable-magnification viewing and aiming scope having zoom lenses. The optics of such a viewing and aiming scope allow the magnification, and thence the field of view, to be controllably changed, so that the user can continuously view the scene through the scope, but the field of view of the scope is still limited.
In some situations, such as a soldier fighting in modern urban warfare, the rifleman is most effective in close-range situations, typically less than 50 meters to the target, when the target is viewed at unity magnification (i.e., 1×) through a non-magnifying reflex viewing and aiming scope used with both eyes of the user open. The reflex scope has an illuminated dot pattern that improves the rifleman's response and precision in emergency situations. However, the field of view is typically restricted to less than 10 degrees, which is significantly less than the field of view of the unaided eye. For intermediate ranges, typically 50-300 meters to the target, the user is more effective when viewing the target through a moderate-magnification viewing and aiming scope of about 2×-6× magnification, using one eye.
There is thus a conflict between requirements for different types of situations. Several different possible approaches and solutions have been proposed. It is not practical to carry two different types of viewing and aiming scopes to be interchanged according to the situation, because events may occur very quickly. In some designs, two viewing and aiming scopes are mounted together, which greatly increases the weight of the weapon and scope. Switching between two-eye, non-magnifying sighting and one-eye, magnified sighting may be difficult and confusing. In the Bindon approach, both eyes are open, and the user views the scene through one unaided eye and through one eye looking through a single viewing and aiming scope. The untrained user can be easily confused and disoriented due to the differences in magnification of the scene viewed by the unaided eye and the aided eye.
As mentioned above, the higher the magnification of the device, the smaller is the field of view available for the aided eye. Typically, a field of view of only 4-7 degrees is available for the aided eye when using a viewing scope according to Bindon's concept. Zoom viewing and aiming scopes require a relatively long time to zoom through the magnification range and for the user to adjust to the different scene and field of view at different magnifications. In particular, the user must be aware when changing magnification that the eye relief also changes, and an additional movement of the head either toward or away from the scope is required to see the maximum available field of view. Zoom viewing and aiming scopes also have poorer optical performance than single-magnification viewing and aiming scopes. In yet another approach, a split-field of view viewing and aiming scope has a higher magnification in the center of the viewing area and a lower magnification on the outer portions of the viewing area. The full target image is not seen for either the higher magnification or the lower magnification, and there can be blind spots between the two portions of the image.
There thus remains a need for an approach to multi-magnification viewing of a scene, particularly for close-in and intermediate-ranges such as encountered in urban warfare and other optics applications. The present invention fulfills this need, and further provides related advantages.